[FFmpeg-devel] [PATCH] lavu: add av_bprintf and related.

Nicolas George nicolas.george at normalesup.org
Sun Feb 19 10:40:17 CET 2012


Signed-off-by: Nicolas George <nicolas.george at normalesup.org>
---
 libavutil/Makefile |    2 +
 libavutil/bprint.c |  136 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 libavutil/bprint.h |  120 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 258 insertions(+), 0 deletions(-)
 create mode 100644 libavutil/bprint.c
 create mode 100644 libavutil/bprint.h

diff --git a/libavutil/Makefile b/libavutil/Makefile
index 6d78bd5..ac3eed0 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -10,6 +10,7 @@ HEADERS = adler32.h                                                     \
           avstring.h                                                    \
           avutil.h                                                      \
           base64.h                                                      \
+          bprint.h                                                      \
           bswap.h                                                       \
           common.h                                                      \
           cpu.h                                                         \
@@ -47,6 +48,7 @@ OBJS = adler32.o                                                        \
        audioconvert.o                                                   \
        avstring.o                                                       \
        base64.o                                                         \
+       bprint.o                                                         \
        cpu.o                                                            \
        crc.o                                                            \
        des.o                                                            \
diff --git a/libavutil/bprint.c b/libavutil/bprint.c
new file mode 100644
index 0000000..88e2a2e
--- /dev/null
+++ b/libavutil/bprint.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2012 Nicolas George
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include "bprint.h"
+#include "common.h"
+#include "error.h"
+#include "mem.h"
+
+#define av_bprint_room(buf) ((buf)->size - FFMIN((buf)->len, (buf)->size))
+#define av_bprint_is_allocated(buf) ((buf)->str != (buf)->reserved_internal_buffer)
+
+static int av_bprint_grow(AVBPrint *buf, unsigned new_size)
+{
+    char *old_str, *new_str;
+
+    if (buf->size == buf->size_max)
+        return AVERROR(EIO);
+    if (!av_bprint_is_complete(buf))
+        return AVERROR_INVALIDDATA; /* it is already truncated anyway */
+    if (!new_size)
+        new_size = buf->size > buf->size_max / 2 ? buf->size_max :
+                                                   buf->size * 2;
+    old_str = av_bprint_is_allocated(buf) ? buf->str : NULL;
+    new_str = av_realloc(old_str, new_size);
+    if (!new_str)
+        return AVERROR(ENOMEM);
+    if (!old_str)
+        memcpy(new_str, buf->str, buf->len + 1);
+    buf->str  = new_str;
+    buf->size = new_size;
+    return 0;
+}
+
+void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max)
+{
+    unsigned asize = (char *)buf + sizeof(*buf) - buf->reserved_internal_buffer;
+
+    if (size_max == 1)
+        size_max = asize;
+    buf->str      = buf->reserved_internal_buffer;
+    buf->len      = 0;
+    buf->size     = FFMIN(asize, size_max);
+    buf->size_max = size_max;
+    *buf->str = 0;
+    if (size_init > buf->size)
+        av_bprint_grow(buf, size_init);
+}
+
+void av_bprintf(AVBPrint *buf, const char *fmt, ...)
+{
+    unsigned room;
+    char *dst;
+    va_list vl;
+    int add;
+
+    while (1) {
+        room = av_bprint_room(buf);
+        dst = room ? buf->str + buf->len : NULL;
+        va_start(vl, fmt);
+        add = vsnprintf(dst, room, fmt, vl);
+        va_end(vl);
+        if (add <= 0)
+            return;
+        if (add < room)
+            break;
+        if (av_bprint_grow(buf, 0))
+            break;
+    }
+    add = FFMIN(add, UINT_MAX - 5 - buf->len);
+    buf->len += add;
+}
+
+void av_bprint_chars(AVBPrint *buf, char c, unsigned n)
+{
+    unsigned room, real_n;
+
+    while (1) {
+        room = av_bprint_room(buf);
+        if (n < room)
+            break;
+        if (av_bprint_grow(buf, 0))
+            break;
+    }
+    if (room) {
+        real_n = FFMIN(n, room - 1);
+        memset(buf->str + buf->len, c, real_n);
+        buf->str[buf->len + real_n] = 0;
+    }
+    buf->len += FFMIN(n, UINT_MAX - 5 - buf->len);
+}
+
+void av_bprint_finalize(AVBPrint *buf, char **ret_str)
+{
+    unsigned real_size = FFMIN(buf->len + 1, buf->size);
+    char *str;
+
+    if (ret_str) {
+        if (av_bprint_is_allocated(buf)) {
+            str = av_realloc(buf->str, real_size);
+            if (!str)
+                str = buf->str;
+            buf->str = NULL;
+        } else {
+            str = av_malloc(real_size);
+            if (str)
+                memcpy(str, buf->str, real_size);
+        }
+        *ret_str = str;
+    } else {
+        if (av_bprint_is_allocated(buf))
+            av_freep(&buf->str);
+    }
+    buf->size = real_size;
+}
+
diff --git a/libavutil/bprint.h b/libavutil/bprint.h
new file mode 100644
index 0000000..7303435
--- /dev/null
+++ b/libavutil/bprint.h
@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2012 Nicolas George
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_BPRINT_H
+#define AVUTIL_BPRINT_H
+
+#include "attributes.h"
+
+/**
+ * Define a structure with extra padding to a fixed size
+ * This helps ensuring binary compatibility with future versions.
+ */
+#define FF_PAD_STRUCTURE(size, ...) \
+    __VA_ARGS__ \
+    char reserved_padding[size - sizeof(struct { __VA_ARGS__ })];
+
+/**
+ * Buffer to print data progressively
+ *
+ * The string buffer grows as necessary and is always 0-terminated.
+ * The content of the string is never accessed, and thus is
+ * encoding-agnostic and can even hold binary data.
+ *
+ * Small buffers are kept in the structure itself, and thus require no
+ * memory allocation at all (unless the contents of the buffer is needed
+ * after the structure goes out of scope). This is almost as lightweight as
+ * declaring a local "char buf[512]".
+ *
+ * The length of the string can go beyond the allocated size: the buffer is
+ * then truncated, but the functions still keep account of the actual total
+ * length.
+ *
+ * Append operations do not need to be tested for failure: if a memory
+ * allocation fails, data stop being appended to the buffer, but the length
+ * is still updated. This situation can be tested with
+ * av_bprint_is_complete.
+ *
+ * The size_max field determines several possible behaviours:
+ *
+ * size_max = -1 (= UINT_MAX) or any large value will let the buffer be
+ * reallocated as necessary, with an amortized linear cost.
+ *
+ * size_max = 0 prevents writing anything to the buffer: only the total
+ * length is computed. The write operations can then possibly be repeated in
+ * a buffer with exactly the necessary size
+ * (using size_init = size_max = len + 1).
+ *
+ * size_max = 1 is automatically replaced by the exact size available in the
+ * structure itself, thus ensuring no dynamic memory allocation. The
+ * internal buffer is large enough to hold a reasonable paragraph of text,
+ * such as the current paragraph.
+ */
+typedef struct AVBPrint {
+    FF_PAD_STRUCTURE(1024,
+    char *str;         /** string so far; or NULL if size == 0 */
+    unsigned len;      /** length so far */
+    unsigned size;     /** allocated memory */
+    unsigned size_max; /** maximum allocated memory */
+    char reserved_internal_buffer[1];
+    )
+} AVBPrint;
+
+/**
+ * Init a print buffer
+ * @param buf        buffer to init
+ * @param size_init  initial size (including the final 0)
+ * @param size_max   maximum size;
+ *                   0 means do not write anything, just count the length;
+ *                   1 is replaced by the maximum value for automatic storage
+ */
+void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max);
+
+/**
+ * Append a formated string to a print buffer
+ */
+void av_bprintf(AVBPrint *buf, const char *fmt, ...) av_printf_format(2, 3);
+
+/**
+ * Append n times char c to a print buffer
+ */
+void av_bprint_chars(AVBPrint *buf, char c, unsigned n);
+
+/**
+ * Tests if the print buffer is complete
+ * It may have been truncated due to a memory allocation failure
+ * or the size_max limit (compare size and size_max if necessary).
+ */
+static inline int av_bprint_is_complete(AVBPrint *buf)
+{
+    return buf->len < buf->size;
+}
+
+/**
+ * Finalize a print buffer
+ * The print buffer can no longer be used afterwards,
+ * but the len and size fields are still valid.
+ * @arg[out] ret_str  if not NULL, used to return a permanent copy of the
+ *                    buffer contents, or NULL if memory allocation fails;
+ *                    if NULL, the buffer is discarded and freed
+ */
+void av_bprint_finalize(AVBPrint *buf, char **ret_str);
+
+#endif /* AVUTIL_BPRINT_H */
-- 
1.7.9



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